How old is the chain? Could it be worn out? Maybe that adaptor on the front sprocket isn't centred? It's getting really close now mate, The cool thing about seeing the light at the end of the tunnel is you just want to get the thing finished and progress happens in leaps and bounds. There's still plenty of nice riding days left this summer!

Just thinking it thru logically, with everything else you've checked like them running true, the only thing I can think of is that one of your sprockets is not a 'perfect circle' ie. that it is ever so slightly oval somewhere, or off centre. Could that be a possibility?If it's a possibility, is where a way to check that? ie. running something out from the exact centre of the sprockets to the outside diameter, sorta like dividers but would need to be something that worked for this situation...? Or measurements from centre?

ok so the chain is new the front sproket is perfect and it seem to be consistent with the rear spoket location ive checked both sprokets for run out with a pointer atached to the frame and cant see any thing ov concern on both planes fuck it i wanna take it for a spin to morow ill get back in the shed in a hr or so and see if i cant crack itany more suggestions????

maybe try spinning it & try observing what is 'different' when it hits the tight spot; & maybe play around with moving it right on the tight spot & see if you can see what's causing it? may become evident as you keep looking. you can always use my way...pray

Mike Ive never owned a bike yet that didn't have a tight spot somewhere in it.The trick is to adjust the chain at the tight spot for the correct chain tension mate.Hope that helps.

arhh shit like this pisses me off its not a massive tight spot humm thinks ill get my ass out there in a min mabe ill get it running a foreget about the chain alltogether brettive looked at the chain from every angle tight not tight grrrr humm praying ill take a pass on that he he